This invention relates to a setting circuit for use with a temperature regulator or the like, and more particularly to a digital setting circuit wherein a straight-line-segment approximation of the nonlinear temperature-resistance characteristic of a measuring resistor is provided. In a second embodiment, a straight-line-segment approximation of the nonlinear temperature-electromotive force of a thermocouple is provided.
For temperature regulation performed through the comparison of the temperature sensed by a measuring resistor or a thermocouple and a set point temperature, the analog setting technique employing a potentiometer is adopted for the most part. In such a setting technique, the nonlinearity of the measuring resistor or the thermocouple can easily be compensated by properly calibrating the indicator scale of the instrument. When a digital setting technique is adopted, however, such nonlinearity raises a problem.
Digital linearization of this nonlinearity has been the only solution provided by the prior art, and a setting circuit wherein a straight-line-segment approximation of the nonlinearity in the digital fashion is provided on the setting side has not been suggested yet.
It is therefore the object of this invention to provide a digital setting circuit wherein a straight-line-segment approximation of the operating characteristic of a sensor, such as the temperature characteristic of a measuring resistor or the temperature-electromotive force characteristic of a thermocouple or the like, is provided by means of a digital setting arrangement built in a bridge circuit.